Adding bleeder valve to cooling system.

[ryanmcgrim]

So finally got the heater core out again, and got the black plastic plug out of the passageway. I can't believe this was stuck so far into the heatercore. I'm surprised the restricted flow hasn't overheated the engine. Heat is supercharged now. So glad to have it working again. Thanks to everyone who pointed me to the answer. I feel like an imbecile.